The invention relates to a method and apparatus for mapping the vertical heat flux of a geothermal field, and more particularly to a rod heat-flux transducer for in situ probing of the vertical heat flux under steady state conditions.
The thermal properties of earth are of considerable importance to the geologist engineer, and others engaged in the study and application of the earth sciences. Geothermal heat flux is a parameter of particular importance in efforts to develop geothermal power as a source of energy because a first step in such development relates to the assessment of the amount of energy available in the earth at particular locations.
A convenient way to determine heat flux in situ requires drilling a borehole, or using an existing borehole, to lower a transducer to desired depths in the earth. This technique is referred to in U.S. Pat. No. 3,714,832. While the technique is basically sound, there are problems because the cased or uncased walls are so irregular as to prevent a transducer of any length to be inserted, particularly if the transducer is to be in physical contact with the walls in at least two vertically displaced points in order to measure thermal gradients. Different techniques have been utilized to overcome this problem, such as the use of a spring device to keep the transducer sensors in contact with the wall, as disclosed in U.S. Pat. No. 3,714,832, or the use of a pad member as disclosed in U.S. Pat. No. 3,807,227. Resorting to these techniques has resulted from a belief that it is necessary for the transducer to have physical contact with the borehole walls.